Patent GB-488895-A (GB)
Title: Improvements in or relating to electric resistance welding machine
IPC: B23K11/04
Filed: 1937-08-03
Abstract: 488,895. Making welded chains; hydraulic machines. AMERICAN CHAIN & CABLE CO., Inc. Aug. 3, 1937, No. 21372. Convention date, Aug. 22, 1936. [Class 93 (iv)] [Also in Group XXIX] In an electric resistance welding-machine for welding together a pair of elements such as the ends of chain links which are normally sprung apart, the elements are pressed together and a welding current passed through the junction, the pressure being automatically reduced to maintain a lower pressure on the elements while the welding current is applied. A pulley 11 drives through reduction gears 12 and clutch 13 a main shaft 14 which through Geneva mechanism 16 imparts intermittent movement to a shaft 15 geared to a shaft carrying a sprocket wheel 20 which positions the links at the welding point. The chain also passes over guide pulleys 22 ... 25, Fig. 2, through a trimmer 26 and over a sprocket driven from the shaft 15 through spiral gears 34. Alternate links are welded during the first passage of the chain through the machine and the remaining links by a second passage. The sides of the link are pushed together at the welding point by two push rods, one of which, 38, is secured to a carriage 40 actuated by a cam 42 on a shaft 43, while the other 50 is actuated hydraulically. The push rod 50 passes through abutment members 75, 76, Fig. 3, mounted in a slidable carriage 52 and carries a collar 74 which moves the carriage when the lost-motion between the abutments has been taken up. The rod 50 is secured to a cross-head 54 and carries an inner sleeve piston 60 enclosed by other sleeve pistons 57 ... 59 working in a fixed cylinder 56. If the pistons 57 ... 59 are free, maximum pressure is imparted to the cross-head 54 when fluid is admitted to cylinder 56, but means are provided for arresting one or more of the pistons to reduce the pressure on the cross-head at a predetermined point. This is effected by an adjustable finger 61 having a hub portion which always engages the outer cylinder 57 and a finger portion which may be positioned to engage one or both of abutment lugs carried by the pistons 58 and 59. The collar 74 preferably engages the abutment 76 when the selected piston sleeves are arrested by the stop 61 so that the further movement under reduced pressure is accompanied by advance of the carriage 52. Insulated thrust pins 82 are mounted in the push rod for engagement with the work. The cross-head 54 is connected by the rods to another cross-head 86 which is under continuous hydraulic pressure in cylinders 88 tending to withdraw the rod 50. The cylinders 88 are formed in the cylinder block 55. Welding current is supplied by two pairs of electrodes 100, 101 arranged on opposite' sides of the joint. The electrodes 100 are carried by a pair of arms 102 pivoted at 104 and moved apart at their outer ends to close the electrodes onto the work by cams 106 on the shaft 43, which actuates the push rod 38. Springs 110 may yield when a predetermined work-engaging pressure is attained. The electrodes 101 move with the push rod 50 during the welding operation and are carried by arms 112 pivoted at 113 on the carriage 52. These electrodes are normally spread apart by a spring 116 but are closed onto the work by hydraulic pressure in a cylinder 119 having opposed pistons 120 connected to one of a series of spaced holes 133 in extensions of the levers 112. The duration of the welding current is controlled automatically. For this purpose a lever 142 is pivoted on a fixed bracket and carries a contact 146 coacting with another contact 147. A solenoid 150 is carried by the vertical lever arm and when the solenoid is actuated it locks an arm 154 pivoted to the carriage so that when the carriage moves the lever 142 is rocked and makes contact 147 to open the transformer primary circuit 157 and stop the welding current. A circuit-breaker 164 is adapted to be closed by a solenoid 165 in a shunt circuit including a switch 168 which is opened by another solenoid 169 when the contact 147 is closed, thus allowing a spring 175 to open the circuit-breaker. When the switch 168 is closed a double-pole switch 177 may be closed either manually or by a cam on shaft 14 to energize solenoids 150 and 165, thus closing the circuit of the transformer primary. The switch 177 is closed when the joint in the link has been closed by the push rod 50 and as the weld is rendered plastic by the current the carriage 52 advances to a predetermined degree until the contact 147 causes opening of the switch 168 to break the transformer circuit. After the weld has been formed it is swaged by hammer levers 180 actuated by a cam 184 driven through gearing from the shaft 14. The trimmer 26, which removes burrs by means of shearing cutters is operated by a cam 190 and bell-crank levers 191. The hydraulic circuit, Fig. 8, is supplied by a pump 196 which by means of a spring-controlled byepass valve gives a predetermined pressure indicated by a gauge 202, and supply to the cylinders 59 and 119 is controlled by spring-closed valves actuated by cams 95, 131 respectively on the shaft 14. In operation the push rods are withdrawn from a. welded link and the sprocket 20 and 28 rotated to position the next link. The push rod 38 is then advanced by its cam and the electrodes 100 closed on the work and then the cylinder 56 is put under pressure to advance the push rod 50 and cylinder 119 actuated to close the electrodes 101. The cam 179 closes switch 177 and energizes the transformer. Clutch 13 now disengages and arrests the shaft 14. As the link softens the push rod 50 and carriage 52 advance together until the current is cut off as described above. After the weld has cooled, the clutch 13 is re-engaged to cause withdrawal of the electrodes and the swaging and trimming operations, after which the clutch automatically disengages.